The principal objectives of this project are part of the ongoing effort identifying antiplaque and anticaries agents suitable for short-term clinical investigation, as well as, to develop methods for assessing the clinical potential for these agents. Methods were developed for measuring the pH response in rat plaque following a flushing of their dentition with a sucrose solution. In vivo methods were difficult. However, a post-mortem method was simple, reliable and exhibited the expected pH decrease. The pH drop appeared to be less in plaque covering fluoride-rich enamel than in that covering fluoride-poor enamel. Fluoride enrichment of the enamel was facilitated by pretreatment of the dentition with a solution of diacalcium phosphate dihydrate. Consequently, it was possible to test the effects of enamel-bound fluoride on the pH, lactate and microbic levels in plaque and on the incidence of dental caries. Enamel bound fluoride appeared to inhibit the drop in pH levels. Confirmatory studies are in progress.